Heir Audio recently launched their first two universal IEMS, the 3.Ai og 4.Ai. They are based on Heir’s custom 3.A and 4.A. As their names might imply, these IEMs have 3 and 4 BA drivers respectively. 3.A(i) is the “fun” musical model and 4.A(i) is the correct and analytical sibling. The Ai models are technically completely identical to the custom editions. Same drivers, same poured acryllic shell. The only difference is that where the 3.A and 4.A are full customs, their Ai brethren have a 6mm nozzle with accompanying silicone/rubber tips. This should mean that as long as you get a proper seal, the Ai should sound identical to its full custom counterpart. To my ears, full customs will always beat universals when it comes to comfort, but the resale value is higher on universals - and they allow you to share the experience with your friends. The Ai models are both made with “Deep Purple” shells, a very dark, almost black shade of purple. You can see the drivers inside them in sufficient lighting but they’re not exactly display cases for technophiles. Like the full customs, the Ai models feel extremely sturdy, thanks to their solid acryllic construction. Not flimsy and brittle like the thin plastic shelled competition - Westone, I’m looking at you. The broad stem might reduce the number of available aftermarket tips (I prefer Shure Olives for my universals) but it sure feels more robust than the thin stem of my FS Atrios. I’ve never broken an IEM stem myself, but I’ve seen it happen to others. The robust build and the removable/user replaceable cables should ensure that your Heir universals will last you a very long time - unless you lose them because they’re so tiny! Here’s a picture of them next to my customs:

On both the 3.Ai and 4.Ai the faceplates are real wood inlays, made from amboyna burl. As usual with any product bearing the Heir logo, the craftmanship is absolutely stunning. The wood has an amazing structure and (naturally) a very organic look with no two Ai units looking exactly the same.

To allow you to safely transport these little gems, you get an Otterbox case that holds the iems as well as the stock cable, a cleaning tool, a selection of tips and two Heir Audio rubber bands for your iDevice+amp portable rig. The 3.Ai and 4.Ai are available for pre-order from the Heir Audio website at $299 and $399 respectively. You can add the seriously nice Magnus 1 cable for an additional $110. The stock cable isn’t bad by any means, but the Magnus 1 with its 4 tinsel wire SPC conductors sounds great and is hands down the most flexible cable I have ever tried. Check out Project86’s review of it here. I use it on my 8.A and even after audiotioning the TWag V2, Toxic Cables Silver Poison and a slew of other cables, I’ll stick to the Magnus. It was a no-brainer upgrade for the 8.A (I even got one for my HD650’s as well!) but adding 25-30% to the total cost of the Ai’s to get a nicer cable might require a little more consideration. All my listening to the Ai’s for the purpose of this review was done with the stock cable.

From the first go, the 3.Ai reminded me of the sound from my 8.A customs - A slightly warm presentation with solid bass. Right out of the box the treble was a bit harsh, but this has now calmed down after some hours of playing, even though it is more aggresive than the treble from the 8.A. With the 3.Ai playing rap, dancehall or electro it’s hard not to grin ear-to-ear. There’s a slightly boosted bass that doesn’t murk up the midrange and the presentation is as dark as my FS Atrios. The Atrios go deeper but the 3.Ai is a much better headphone for all-round usage while the Atrios are more comfortable with the bass-heavy electronic genres. The 3.Ai has more of an “up front” presentation, dragging you into the music unlike the laid back Atrios. The lively sound from the 3.Ai makes them an excellent choice for rock and electro. The fact that the look amazing and are VERY compact is just a bonus. Rammstein’s song “Waidmanns Heil” (Huntsman’s salute) starts out with a Parforce horn, followed by fast drums and then Till Lindemann’s instantly recognizable vocals. All of these are easy to tell apart while it all comes together in a very musical presentation. My go-to track for testing the bass, “Chameleon” by TrentemÝller flows effortlessly from the 3.Ai, creating a beautiful, intricate soundscape on top of a thumping, deep foundation of constantly changing bass. The little details in the track are never lost or overpowered by the bass and the 3.Ai just gets it all right. The Atrio has (a bit) more bass but the 3.Ai offers a vastly more complex soundscape with layer upon layer of sound. Above And Beyond’s album “Group Therapy” is also very enjoyable on the 3.Ai. Vocals are allowed to soar while the keyboards flow and the bass is pumping beneath it all but stays in its place. Jumping to the FS Atrios I get more weight to the bass, but then the midrange and treble suddenly takes the back seat and the bass steals the focus. The 3.Ai has a far more balanced presentation, with only a slightly boosted bass that still stays where it should, never overpowering the midrange and treble.

I often find myself coming back to Rammstein when I’m listening to the 3.Ai. The combination of deep, punchy drums and the crystal clear treble works extremely well with their tanzmetal (Dance metal). Especially “Wiener Blut” (Vienna Blood) with its deep, thunderous drums and shredding guitar riffs, the all-encompassing keyboard setting the mood and building the soundscape around the characteristic voice of Till Lindemann, is a pleasure with the 3.Ai. Much to the amusement of my co-workers, air-drumming usually ensues. A complete change of genre to Dawn Langstroth leaves me wanting for her vocals to be a bit more forward in the mix, but everything still sounds good. The 3.Ai can be described as a fun (but never too fun) all-round IEM especially suited to rock and electro. Sadly, I no longer have the Westone 3 for a direct comparison but I remember it as being duller than this. Good, but less lively and sparkly. If I were to compare the 3.Ai with a full-sized headphone it would be the Ultrasone Pro 2900: Good bass and sparkly highs while retaining the mids. If we start comparing build quality, look and feel, the 3.Ai just leaves the competition in the dust.

Heir Audio 4.Ai is the balanced “correct” IEM and the universal version of the 4.A custom IEM. Two BA drivers for the bass, one for the midrange and one for the treble might lead you to believe that this is a bass heavy IEM, but that is not the case at all. The bass doesn’t go as deep as the 3.Ai or my 8.A. The 4.Ai is ruler flat and accurate but achieves this without ever being dull or boring. Their presentation is very involving, making it almost impossible to use them just for blocking out noise - they demand your attention, but manages to do so without ever becoming too aggresive or intrusive. How The Wizard achieves this insanely difficult balance has baffle me since the first moment I heard the 4.Ai. In exchange for your undivided attention the 4.Ai rewards you with gobs and gobs of details throughout the audible spectrum that combine to give you a great sense of the individual placement of the instruments. On tracks with well-recorded vocals you can get the sense of really being there in the studio with the singer. On the album “Film Music by John Williams” by The City of Prague Philharmonic Orchestra I’m able to pinpoint the location of the individual (groups of) instruments in the concert hall, easily distinguish the strings from the woodwinds and enjoy the brass horns while the kettle drums lays down the foundation. (Phantom Menace, Duel of the Fates). All these details are served for me on a silver platter, the 4.Ai pulls me into the music as opposed to my 8.A that has a similar level of detail and resolution but requires that I listen for it myself. With the 8.A I can listen to Hans Zimmer’s excellent soundtrack to The Last Samurai as a sonic backdrop to my work whereas the 4.Ai leaves me no choice but to let myself be carried away by the arrangement of strings and woodwinds, work be damned.

I’ve owned the AKG K271 mk II (twice!) and while they are neutral and good with strings, they are neither immersive or exiting. At the risk of offending K271 mk II fans I’ll even go as far as calling them rather dull. I thought this was the price one had to pay for neutrality, but the 4.Ai has proved me wrong. They’ll do fine with bassy music as well, but I find them lacking a bit of weight behind the punches compared to the 3.Ai, the Atrio and my 8.A. On the track “Take The Power Back” by Rage Against The Machine the drum hits should feel like a roundhouse kick but on the 4.Ai they’re more like regular punches. The sound is there (and spot on) but I find the physical sense of impact to be a bit lacking. You do, however, get every single riff from the guitars, the cymbals have the real “ring” to them and Zach De La Rocha sounds exactly as angry as opressed as only he can. Don’t get me wrong, the 4.Ai aren’t bass light as the ATH-W1000 or the aforementioned AKG’s, I would just have liked some more weight behind the bass. The great level of detail and the fast drivers makes the 4.Ai a great choice for a very, very wide range of music, but their presentation also means that poorly recorded albums will be less enjoyable. I have a 24/96 vinyl rip of the album “Parsley, Sage, Rosemary and Thyme” by Simon and Garfunkel (1966) and it’s a nice listen on my 8.A where I only hear the noise and cracking if I deliberately listen for it. With the 4.Ai I almost see the vinyl turning and the needle skipping over the scracthed up old record. Instruments and voices still sound great, but for vintage recordings the 4.Ai would not be my first choice. Going forward 20 years to Paul Simon’s solo album “Graceland” the technical quality is far, far better and it is impossible not to enjoy with the 4.Ai. If you like Paul Simon, that is. The same goes for female vocals - Rebecca Pidgeon, Louise Rogers, Norah Jones and my rocksteady go-to girl for testing gear: Dolores O’Riordan as the voice of The Cranberries. Their song “No Need To Argue” from the album bearing the same name is beautifully haunting and an absolute pleasure on the 4.Ai.

Conclusion: I wouldn’t want to be running Westone, Shure or Etymotic right now. Off course they won’t come falling down like a house of cards just because a newcomer launches a set of universals, but the 3.Ai wipes the floor with just about any other “fun” IEM and does that at only $299. Compare that to the (sort of dull) Westone 3 costing only $20 less on Amazon, with an inferior build, non-removable cables and no Otterbox case. I know which I’d prefer just from the sound, the accessories, superior build and great looks are just a bonus. As for the 4.Ai I believe them to be the best universal you can buy at the moment. At $399 they match the detail levels and clarity of my $1100+ 8.A’s and beat the hell out of just about anything else. A friend of mine described them as disturbingly close to his JH13 and the best universals he had ever heard. I haven’t had the pleasure of the JH13 but I sure do agree with the last part of his statement.

Disclaimer: This review has also been posted on Head-fi.org. The Heir 4.Ai are my own, the 3.Ai was kindly lent to me by Heir Audio for this review. But they won't be going back as my friend bought them after trying them.